This invention relates to cameras with interchangeable lens units, and more particularly to an index mechanism for controlling orientation of a unit bayonet relative to a diaphragm in the unit when decoupling the unit from a camera body thereby to facilitate later coupling of the unit by establishment of an operative connection between the diaphragm and a control mechanism which is positioned in the camera body.
It is known to provide an interchangeable lens unit, having a coupling element or bayonet fixedly mounted on the housing thereof, with an adapter shell of the unit which is rotatable relative to the housing to enable a diaphragm to cooperate with a control mechanism incorporated in a camera body after the bayonet is rotated in a tightening direction. It has been common practice to provide a significant clearance between the bayonet of the unit and a bayonet on the camera body so that coupling and decoupling are facilitated. With a mechanical unit of the type described, however, this clearance often leads to disorientation of the unit housing from the adapter shell when decoupling the unit from the camera body. As a result, later coupling is made impossible as there occurs mechanical interference between an angular position adjusting pin and the wall of the camera housing near a receptor for the pin and between the signal members and the operational members of the control mechanism.
It is an object of the present invention, to eliminate such conventional drawbacks and to provide a camera with an interchangeable lens unit which is detachable after the coupling element of the unit is accurately oriented relative to an angular position adjusting pin on the adapter shell which is rotatable relative to the unit housing and coupling element.
Another object of the present invention is to provide a coupling arrangement between a lens unit and a camera body provided with an index mechanism for controlling the orientation of the unit relative to the camera body during decoupling.
Still another object of the invention is to provide an interchangeable lens unit capable of being reliably and quickly coupled with a camera body while preventing the occurrence of mechanical interference between a signal member of a diaphragm in the unit and an operational member of a control mechanism for the diaphragm in the camera body.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.